
ATM Segmentation and Reassembly Controller—SAR
The Bt8230 Segmentation and Reassembly Controller (SRC) incorporates a host
interface, ATM Adaptation Layer processing, and line interfaces in a single device.
The feature set includes a PCI bus interface, segmentation and reassembly control-
lers, a local memory controller, a DMA coprocessor, and an automatic scheduling
algorithm. Each segmentation channel manages an independent bit rate of up to 200
Mbps per channel for simplex connections. This feature set makes the Bt8230 ideal
for file server ATM adapters, routers/hubs, and other Wide Area Network (WAN)
applications. The PCI bus interface makes the SRC suitable for workstation network
interface cards (NICs) as well.
The Bt8230 supports sixteen thousand open connections simultaneously with
robust Operation and Maintenance (OAM), signaling, and Interim Local Management
Interface (ILMI) features. Other key features include support for random Virtual Path
Indicator/Virtual Channel Indicator (VPI/VCI) assignment, interleaved AAL5 and
AAL3/4 Segmentation and Reassembly (SAR), and termination of signaling and ILMI
into local memory to maintain management connections independently. The Bt8230
fulfills all the requirements of the ATM Forum UNI 3.1 standards and the related ANSI
and ITU standards. The device is pin-compatible with the Bt8233 SRC which sup-
ports new traffic management algorithms for ABR service as defined in TM 4.0.
The Bt8230 architecture provides several implementation options, allowing users
to balance the cost and functions of their systems. In stand-alone mode, the Bt8230
is capable of full line-rate performance, presenting a low-cost option ideal for work-
station ATM NICs. Combined with the Bt8222 ATM Receiver/Transmitter, the Bt8230
delivers an ATM solution capable of full-duplex operation at 155.52 Mbps without the
cost constraints of using a large amount of local memory to buffer incoming ATM
cells. When using the local processor, host driver software needs decrease and host
performance is improved since more control functions are handled locally. In slave
UTOPIA mode, the Bt8230 can be connected directly to an ATM backplane for appli-
cations exceeding 155 Mbps.
The Bt8230EVS evaluation system provides a working reference design and an
example software driver. It also has facilities for generating and terminating ATM traf-
fic.
PCI
Bus
32
UTOPIA or
Bt8222 ATM
Interface Rx/Tx
32
Local
Processor
Bus
Bt8230
P
C
I
D
M
A
Memory
Arbiter
Control/
Status
Cell
FIFO
Reassembler
Segmenter
Scheduler
Timer
Counters
Bt8230
Distinguishing Features
Simultaneous ATM and SMDS SAR
ATM Forum UNI 3.1 compliant
Pin-compatible with TM 4.0 options
AAL0, AAL3/4, and AAL5 SAR
Formats AAL3/4 and AAL5 CPCS fields
and performs all checks
Performance monitoring per GR-1248
and ITU I.610, dated 3/93
Supports 16,384 active Virtual Circuit
Channels (VCCs)
Robust per-VCC statistics supports
SNMP MIB requirements
Internal MIB counters
155 Mbps full-duplex throughput
UTOPIA master, UTOPIA slave, or
Bt8222-compatible ATM PHY interface
PCI host interface (master and slave
mode), Revision 2.0
Automatic scheduling algorithm oper-
ates individually on each channel
Host or local segmentation and
reassembly
VBR and UBR traffic types
Scatter/gather DMA to host memory
Optional local processor for signaling,
OAM, and ILMI management functions
Zero- or one-wait-state local memory
Boundary scan to facilitate board-level
testing
Low-power CMOS process in a
208-pin PQFP
Complete working reference design,
software, and documentation package
available
Applications
ATM interface for routers and hubs
ATM/PCI interface cards
Test and WAN equipment
Service access multiplexors
Functional Block Diagram